Speed-control apparatus



M. E. LEEDS SPEED CONTROL APPARATUS Dec. 11, 1923. 1,476,824 I FiledJan. 22, 1919 .F'ICi 1 27 FIG: Z. 26 26 25 INVENTOR 37 m cga 2 A TTORNEYPatented Dec. 11, 1923.

UNITED STATES PATENT OFFICE.

MORRIS E. LEEDS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO LEEDS 66NORTH- RUP COMPANY, OF PHILADELPHIA. PENNSYLVANIA, A CORPORATION OFPENN- SYLVANIA.

SPEED-CONTROL APPARATUS.

Application filed January 22, 1919. Serial No. 272,435.

T all whom it'may concern."

Be it known that I, Monms E. LEEDS, a citizen of the United States,residing in the city of Philadelphia, county of Philadelphia, and *Stateof Pennsylvania, have invented a new and useful Speed-Control Apparatus,of which the following is a specification.

My invention relates to speed control apparatus comprising a centrifugaldevice or governor controlling co-acting contacts which may control anysuitable circuit to effect a speed control, but which are employed moreparticularly to control the speed of an electric motor which drives thegovernor.

It is the object of my invention to pro-- vide speed control apparatusof the character referred to which shall be capable with great nicety tocontrol the speed of a device, such as an electric motor and apparatusdriven thereby, whereby the speed fluctuations may be reduced, forexample, to the order of one-tenth of 1% or less, as required, forexample, in a chronograph employed in measurementof flight ofprojectiles.

While my invention is applicable to various types of centrifugalgovernors, it is particularly applicable to apparatus such as disclosedin my prior Patent No. 1,057,- 436 and produces a marked improvement innicety of speed control, in some cases the fluctuation from desired orcritical speed being reduced to one-fifth to one-tenth of. that attainedby apparatus such as described in said Letters Patent.

For an illustration of some of the forms my invention may take,reference may be had to the accompanying drawing, in which:

Fig. 1 is an elevational view, some parts in section, illustrating acentrif al governor embodying my invention an driven by and controllingthe speed of an electri motor.

Fig. 2 is a plan view of one form of spring suitable for my inventionbefore bending the same to the form shown in Fi 1.

lg. 3 is a side elevational. view of the spring of Fig. 2.

Fig. 4 is a fragmentary elevational view illustrating a modified form ofresilient mounting for one of the governor contacts.

Fig. 5 is a fragmentary elevational view of a further modification ofresilient mounting for the governor contact.

Fig. 6 is a diagrammatic view of one of various types of electric motorwhich may be employed and the control thereof by the governor contacts.

Referring to Fig. l, M is an electric motor whose armature or rotor ismounted upon and drives the shaft 1 mounted in the usual bearings 2, 2.Secured to the shaft 1 by the screw 3 is the coupling 4, which may be ofinsulating material, upon which is secured by screw 5 the worm 6 drivingthe gear 7 secured upon the shaft 8 having a bearing in the member 9.The shaft 8 drives any suitable device or mechanism whose speed is to becontrolled with great nicety, though the shaft 1 may directly drive thedevice or mechanism whose speed is to be controlled. The shaft 10coaxial with the motor shaft 1 is secured to the coupling 4 by screw 11.Secured upon the shaft 10 is the cylindrical hub 12 on the supportingmember or bracket 13. On the arm 14 of the bracket 13 there is pivotedat 15 the lever 16 having secured thereto or integral therewith thelever arm 17 preferably screw threaded, upon which is threaded orotherwise longitudinally adjust-ably supported the governor weight 18.The lever arm 17 which with the lever arm 16 may be considered to form abell crank lever, extends preferably substantially parallel with theaxis of the shaft 10. To the lever arm 17 is attached one end of aspring 19, shown under tension, Whose other end is secured to the rod 20extending through an arm 21 of the bracket 13, different tensions beinggiven to the spring 19 according to the position of the rod 20 which issecured in any of its adjusted positions by screw 22.

The movable arm 16 carries the rotary and longitudinally movable contact23 adapted to engage the spr' g mounted stationary contact 24 which aybe the lower surface of the free end of the easily yielding bowed leafspring 25 or a separate contact piece, as shown, secured upon the freeend of the s ring 25, whose other end is secured "to t e verticallyadjustable screw or abutment 26 threaded in the arm 26 which may becarried by. the member 9, a nut 27 looking the screw 26 after-it hasbeen adjusted to suitable position. A suitable stop, as 2 6 carried byscrew 26, may be provided -.brush 3O bears upon the hub 12, of metal,

which is in electrical communication through the metal parts 13, 14 and16 with the contact 23. The brush 30 is mounted in a socket in theconducting member or brush holder 31, the spring 32 keeping'the brush 30in contact with the hub 12. One circuit wire, as 33, is connected to thebrush holder 31, while the other circuit wire, as 34, is connected tocontact 24 through the member 26, screw 26 and spring 25.

The relation of the spring 19 and weight 18 may be made anythingsuitable or desirable, as for procuring a stable, unstable or neutralgovernor, to all of which types of governor my invention is applicable.

The operation is as follows:

The motor M drives the shaft 10 and rotates the bracket or supportingmember 13 and associated parts, the member 9 being sufficiently to therear to allow free rotation. Accordingly the contact 23 rotates inengagement with respect to the stationary contact 24. When the speed ofrotation exceeds a predetermined critical speed, the centrifugal forceexerted by'the Weight 18 causes it to move outwardly from the axis ofrotation in opposition to spring 19, thereby moving the lever arm 17slightly in a counterclockwise direction about the pivot 15, anadjustable stop 16 on arm 21 serving to limit the downward movement oflever 16. The weight 18 is on a short lever arm, while the contact 23 ison a long lever arm, and therefore a slight movement of the weight 18 isaccompanied by a relatively greater movement on the part of contact 23,with the result that upon a slight increase of speed above apredetermined critical speed the contact 23 is withdrawn from engagementwith contact 24, breaking the circuit in which they are included.

The circuit including the contacts 23 and 24 ma be any circuit, as forexample, such asin icated in Fig. 6, where the motor M is shown as aseries motor having the armature A and the series field windings f. Themotor M is supplied with current rom the conductors 35 and 36 extendingfrom any suitable source of current. In series with the motor are theresistances 37 and 38. The conductors 33 and 34 connect the contacts 23and 24 in a circuit shunting the resistance 38, which latter is ineffect cut out of circuit when the contacts 23 and 24 are in engagementWith each other.

The effect is therefore to change the amount of resistance in thecircuit of the motor M as the speed increases above the desired criticalspeed, the motor then slowing slightly, with a resultant reengagement ofthe contacts, with a tendency again to increase the speed of the motor.

- It has been found that a governor such as above described, whether itbe neutral, stable or unstable, but with the stationary contact 24rigidly mounted as illustrated in the above mentioned Letters Patent,does not open and close its contact with the extreme nicety andcertainty sometimes desired.- A properly behaving governor, particularlywhen neutral or unstable, should maintain the contacts in engagementwith each other until the critical speed is reached, and then shouldcompletely and effectually separate the'contacts. -In the case of anunstable governor, at critical speed the centrifugal member should flyout to the extreme limit permitted by its stop. A governor with thestationary contact rigidly mounted as in said Letters Patent does not sobehave, but on the contrary, the resistance at the contacts may varythrough wide limits. In some cases the resistance at the contacts, orwhat may be compared to the resistance at -the contacts, ranges,relatively, from a fraction of an ohm to several hundred ohms, withresultant imperfect or incomplete circuit rupture and im erfection ofcontrol. This is believed to be due to toughening of the contactsurfaces resulting from wear and sparking, causing the contacts to makeintermittent contact and in effeet to bounce on each other or chatter asthey revolve with respect to each other,.due-

to small irregularities in their engaging surfaces. The periods of thebouncing or chattering depend upon the difference between the forceexerted by the spring and the centrifugal force and the moment of themoving system about the pivot, as 15. This difference between the twoforces varies from a relatively strong force at speeds below thecritical speed to practically zero at critical speed.

Whatever causes the bouncing or chattering occurs once for eachrevolution of the rotary contact; and it is believed that in practicebouncing or chattering is caused a plurality of times for eachrevolution. In order that the contacts shall not materially separatefromeach other before critical speed is reached notwithstanding thebouncfiig or chattering, it is necessary that they shall follow eachother quite continuously notwithstanding irregularities in their contactsurfaces. This is accomplished by to elongate the same distance.

making the spring 25 light or weak in the or to longitudinal movement ofcontact 23 Withoutaffecting the governor. For example, spring 25,especially in the governor illustrated, may yield a given short distanceto a force which is about one-half to onetenth the force necessary tocause spring 19 And a similar relation may hold where spring 19 isreplaced by gravity to oppose the centrifugal force exerted by weight18.

The spring 25 and contact 24. as a resilient system, after havingyielded or bounced away from contact 23 must very quickly and promptlyreturn to normal position with respect to contact 23. This isaccomplished by maki g the natural period of the resilient system short.The half period of vibration of the resilient system should be at leastas short as and preferably considerably shorter than the time occupiedfor one revolution of the contact or governor shaft 10. By way ofexample merely, and Without limitation of my invention thereto, it maybe stated that where the governor shaft 1t makes 53 i revolutions persecond, the natural period of a half-vibration of the resilient contactsystem in the direction of longitudinal movement of the contacts, thatis, in a direction longitudinally of the governor shaft, is preferablyat least onetwenty-fifth of a second and may be with advantageone-fiftieth of a second; and it will be understood that the relativeperiod of vibration may be even shorter.

It is also desirable that the mass of spring 25, or of spring 25 withcontact 24. if a contact as 24 be mployed, shall be small, andpreferably so small as not to affect the action or behavior of therotating governor system, as by reaction thereon through Contact 23.

It will be understood, therefore, that my improved results are attainedby using a spring contact system which preferably has small mam andwhich yields readily to the forces incident to the bouncing orchattering or to longitudinal movement of the rotary contact, without,however, materially disturbing the governor as regards the relation ofthe forces exerted by the spring 19 and the weight 18; and further, bymaking the natural period of the resilient sys tem so short that afteryielding or bouncing restoration is so prompt that the contacts may besaid to be substantially continuously in engagement with each other. Bythis arran ment the contact resistance is low and varies but slightly;and when the contacts separate the effectually electrically separate topr uce practically infinite resistance between them.

When contact 24 is omitted, as it may be, the spring 25 itself directlycontacts with contact 23; and in such case the characteristics of theyielding or resilient contact system 25 are the same as those abovedescribed.

While With the contact 24 rigidly mount-- ed as described in saidLetters Patent very small fluctuation of speed is attainable,nevertheless by my improvements herein described the fluctuation inspeed may be reduced to one-fifth or one-tenth of what it is, otherthings being the same, when the contact 24 is rigidly mounted. By themprovements herein described the variation of speed from critical speedmay be reduced to one-tenth of 1%, or even less.

As further improving the operation, the area of contact between contacts23 and 2t is reduced as by making eitherof the contacts, as 23, conicalat its end, as indicated.

In lieu of bowing the spring 25 as indicated in Fig. 1, the same may bedisposed as indicated at 25*, Fig. 4-. a

By preference the spring 250$ Fig. 1 and the springs 25 of Fig. 4 maytaper, aS indicated in Fig. 2, from its large end, where secured to thesupport, to the small end, where a contact as 24 may be attarhed. Thesesprings may also diminish in thlC-KDQSS from the end where secured tothe support to the contact end as indicated in Fig. 3. Figs. 2 and 3show the spring 25 before bending to the form shown in Fig. 1, or asemployed in Fig. 4.

While the bowed spring 25 of Fig. 1 is the preferred form, the contact24 may also be otherwise resiliently mounted, as upon the end of ahelical spring 39, as shown in Fig. 5.

As in the case of Fig. 1, the, contact 24 may be omitted in Figs. 4 and5, and the ends of the springs 25 and 32 themselves contact with therotary contact 28.

The hereinbefore described characteristics of the resilient or yieldingcontact system of Fig. 1 are preferably had also by the systems of Figs.4 and 5.

While it is preferred that the yielding or resilient contact systems,comprising springs 25, 25 and 39, shall be stationary, it will beunderstood that by mere reversal such resilienit or yielding contactsystems may be secured upon and rotate with the governor arm 16 with thecontact surface of such system cooperating with a stationary contact.

What I claim is:

1. Speed control apparatus comprising a centrifugal governor, a contact,a resiliently yielding contact system, said contact and said systemengaging each other in the axis of rotation of the rotating structure ofsaid governor, said system having small mass and having a natural eriodof vibration longitudinall of the axis of rotation of said governorwhich is at least as short as the time of onerevolution of the rotatingstruc; ture of said governor.

2. Spied control apparatus comprising a centrifugal governor, cooperatincontacts controlled by the governor, one ot said contacts rotating withsaid governor and engaging another of said contacts in the axis ofrotation, and a resilient mounting for least one of said contacts havinga natural period of vibration which is at'least as short as the periodof one revolution of said rotating contact, said contacts normally engaging each other and separating upon excess of speed above a predeterminedcritical speed. i

3. Speed control apparatus comprising a centrifugal governor, cooperatincontacts controlled by the governor, one 0 said contacts rotating withsaid governor and engaging anotherof said contacts in the axis ofrotation, and a spring supporting one of said contacts and constitutinga system having a natural period of vibration which is shorter than theperiod of one revolution otsaid rotating contact.

4. Speed control apparatus comprising a centrifugal governor,cooperating contacts controlled by the governor, one of said contactsrotating with said governor and engaging another of said contacts in theaxis of rotation, and a spring supporting one of said contacts yieldingeasily to the cooperating contact and constituting a system having anatural period of vibration which is shorter than the period of onerevolution of said rotating contact.

5. Speed governing apparatus for preventing fluctuation of speed greaterthan one-fifth of 1% comprising a centrifugal governor, a contact, aresiliently yielding contact system, said contact and said systemengaging each other in the axis of rotation of said overnor and one ofthem rotating with sand governor, said system yielding easily in adirection longitudinally of the axis of rotation of said governor, andhaving a natural eriod of restoration in said direction Whic is at leastas short as the time of one revolution of said governor.

6. Apparatus for controlling the speed of an electric motor comprising acentrifugal governor whose speed corresponds with the speed of themotor, and motor control contacts disposed at the axis of rotation ofsaid governor and one of them actuated by said governor, one of saidcontacts comprised in a resilient system having such characteristicsthat speed variation in excess of one-fifth of one per centum isprevented.

In testimony whereof I have hereunto affixed my signature this day ofJanuary, 1919.

MORRIS E. LEEDS,

